That tool is commonly referred to as an air ratchet. They spin fasteners
until the fastener gets snug, then the operator starts turning it as thae
would a normal ratchet.

I never liked using them, or even being around them being used. They're loud
and irritating. In close quarters, they can trap your hand or injure your
fingers.

I prefer to use an air impact wrench, and for small/medium fasteners, the
3/8" drive was very satisfying to use. I don't know that a 3/8" impact
wrench would operate the punch very well though.

Do you realize how slow that type of punch will be for 300 holes? As you
know, you'll need to drill all the locations first.
Then you assemble the punch thru the hole (quickly if you can), then you
need to crank it down fully to punch the 1" diameter and shear the slug free
of the box.

Then you disassemble the punch and clear the slug. Sometimes the slug comes
out easily, other times not so quickly.

This method is a lot of parts handling and it takes time. If you start
dropping the punch parts it goes even slower.

There will still be a sharp edge where the male die/punch part passes thru
the metal, and although the punches don't usually cause much distortion, the
hole edge might be flat, so a step drill might not work as well for
deburring the hole.

Since the metal isn't heavy gage, you might be able to use a drill motor
with some serious torque.

You might want to also have a smaller, lighter drill motor to run the bolt
into the die quickly, then change to the slower drill motor with high
torque.

The only way that I could see the punching portion of the 300 piece job
moving along quickly would be to have at least several punches and a helper.

The 1 cubic foot boxes will take up a lot of workbench space, so a helper
might be able to assemble the punches in holes, and handle moving the boxes.

I'd most likely try to find a shop with some sort of punch press to make the
1" holes.

Hole saws generally aren't fast (or accurate) and they dull quickly if
they're pushed hard. In thin metal, they are prone to snagging and pulling
the workpiece out of whatever is holding it.
They should always be run relatively slow and be used with a cutting
lubricant on metal, which gets messy.

If your drill press would stall while attempting to use a step drill,
rotabroach or hole saw up to 1", then you're probably faced with using a
bolt-type punch.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"K Ludger" wrote in message
...

"K Ludger" wrote in message
...
I've got a job coming up to drill around 300 x 25mm diameter holes in
some powder coated steel electrical enclosures. The metal is 1mm thick,
probably 30 - 35 thou. Punching is out, I need to do this using my drill
press.

I've done a bunch of holes in the past using a step drill, and then spent
almost as much time again deburring the holes. I'de very much like to
avoid using coolant or Trefolex due to the cleanup involved with the
enclosures.

I'd like to drill the holes in one go (ie not pilot then change & drill)
any recommendations as to the best approach or tool that I should use?

thanks


Wow so many replies - thanks to all!

I'm leaning toward drilling a single hole then using a Green Lee or
Bramley punch (wrench driven unfortunately).

My drill press while substantial has been retrofitted with a 1/2 hp single
phase 240V motor and with the current chuck (not morse taper) would not
handle a rotabroach. The enclosures are an off the shelf prefabbed item my
customer uses regularly. They are around 1'x1'x1' and are difficult to
clamp/locate on the drill press. The hole location is not critical within
0.1" will be ok, its for a cable gland to be fitted into.


On the topic of chassis punches, will a 1/2 drive air wrench similar to
the one at the link below drive a Green Lee or Bramley 1" punch?

http://www.toolstation.com/images/li...bbig/45203.jpg

Would using soap / beeswax aid the punching operation?


Many thanks for all of the advice.


Seasons greetings to all.